Products comprising fat-soluble active substances encapsulated in a hydrocolloid matrix find wide spread use in all kinds of human and animal products, such as food, food supplements, beverages, pharmaceutical, agricultural and veterinary products and personal care products. The purpose is to protect the oxidation sensitive active substance from oxygen and other substances, which attack the substance in order to avoid off-flavour and loss of physiological activity, e.g. during transport, and to increase the shelf life of the products.
When encapsulating fat-soluble active substances an important and acknowledged quality parameter is the content of free surface fat. If the product is not substantially free of free surface fat, e.g. if the content of free surface fat in a product comprising polyunsatutared fatty acids (PUFA's) is more than 1-2%, the quality of the product is significantly impaired and the product will quickly deteriorate through oxidation. PUFA-products complying with this quality parameter normally can not hold more than 25-30% of active substance. Besides, products comprising an increased content of fat-soluble active substance must traditionally be produced by using also an increased amount of hydrocolloid.
Hogan et al in J. Agric. Food Chem. (2001) Vol 49, No. 4, pages 1934-1938, describes microencapsulating properties of sodium caseinate when used in emulsions of soy oils. The effect of increasing the oil/protein ratio on protein load is tested, and it appears that increasing the oil/protein ratio from 0.25 to 3.0 resulted in a progressive decrease in microencapsulation efficiency.
Vega et al in Jour. Dairy Sci. (2006) Vol. 89, No. 2, pages 383-401 describes emulsions with oil-to-protein ratios ranging from 0.25 to 5. Surface fat was reduced from 30% to less than 5%, when lactose was added to an emulsion containing 30% oil.
Vega et al in Int. Dairy Jour. (2007) Vol. 17, No. 6, pages 683-695 describes spray drying of an anhydrous milk fat emulsion stabilized by caseinate or milk protein isolate with trehalose or lactose as encapsulants. The solvent extractable surface free fat values for the spray dried emulsions are determined, and it appears that the higher oil-to-protein ratios, the higher surface free fat.
WO 94/01001 describes microencapsulated oil and fat products, wherein a ratio oil-to-caseinat between about 2.25:1 and 2.75:1 is used. The resulting products hold e.g. 25% fat or oil.
WO 01/74175 describes encapsulated oil products with a rather high content of oil of up to 60%. The resulting products have a high content of free surface fat and/or a relatively high content of hydrocolloid.
The object of the present invention is to provide microcapsules having both a high content of fat-soluble active substance and a desirable low content of free surface fat as well as a new process for preparation thereof.
A further object of the invention is to provide microcapsules with a high content of fat-soluble active substance wherein a corresponding increase in the content of hydrocolloid is avoid.
It is a further object of the invention to provide microcapsules having storage and transportation stability as well as mechanical strength and improved performance during the further processing into tablets, extrudates and the like.